Key operated cylinder locks are widely used in various aspects of everyday life. It is often desirable to be able to change a lock. A typical changeable cylinder lock includes an alterable combination of tumbler pins that matches the combination of teeth on a proper key for opening the lock. The lock is changed or re-keyed by altering the combination of the tumbler pins and teething the key accordingly. The keys for opening the lock before and after the re-keying have different teeth, but generally have the same longitudinal groove patterns on their blades. Therefore, the key for opening the lock before the re-keying can also be inserted in the key slot after the re-keying. Further, the keys for opening the lock before and after the re-keying can be formed from the same kind of key blanks, which are usually available in many hardware and locksmith stores. Because of security considerations, the identical groove patterns for keys before and after the re-keying and wide availability of the key blanks for the re-keyed lock are sometimes undesirable.
Accordingly, it would be advantageous to have a method for re-keying a lock that is simple and cost efficient. It is desirable if the key for the lock before the re-keying cannot be inserted into the lock after the re-keying. It is also desirable for the key for the re-keyed lock to have a unique feature that is not readily available on the market. It would be of further advantage to have a simple, reliable, and cost efficient apparatus to implement the re-keying method.